1. Field of Invention
The present invention relates to ballast for rapid-start fluorescent lamps, particularly of a type wherein external cathode heating power is provided during lamp starting, but is automatically removed after the lamp has started.
2. Description of Prior Art
It is known in the art that the liminous efficacy of an ordinary rapid-start fluorescent lamp is substantially improved if the externally-provided cathode heating power is removed after the lamp has started.
One approach to automatically removing externally-supplied cathode heating power from the fluorescent lamp after the lamp has started, is described in U.S. Pat. No. 4,375,608 issued to Kohler. However, the approach described in that patent is extremely complex and costly.
No simple and inexpensive fluorescent lamp ballast with built-in means for automatically removing externally supplied cathode heating power has been previously described in available literature; nor is such a ballast available for purchase.